A stadium field system has been proposed in which a game field using a good natural lawn can be utilized to play soccer and rugby or play other games freely in a roofed stadium. More specifically, a game field having a natural lawn planted on a frame is movably fitted in a trench provided between a field region of a roofed stadium and an outdoor region for growing the natural lawn, and transporting means for running in the trench is provided on the frame such that the game field is alternately moved to both of the field region of the roofed stadium and the outdoor region (see Japanese Unexamined Patent Publication No.HEI4-327868, for example).
According to the prior art, it has been acknowledged that the game field using a good natural lawn can easily be placed also in the roofed stadium, various games such as soccer and rugby can be played on the natural lawn, and the natural lawn can be grown by placement of the game field in the outdoor region. However, a trench having a pit structure for moving the game field is provided between the field region of the roofed stadium and the outdoor region. Therefore, when using the game field in the outdoor region, the trench for movement is remained in the field region of the roofed stadium. For this reason, when using the field region for baseball games, the trench should be blocked to newly form a diamond field for baseball. Furthermore, since the game field employs the transporting means having a truck structure, its thickness exceeds 1 m. Accordingly, it is predicted that a large amount of materials are required to block the deep trench and a lot of time and labor are necessary for taking in and out the materials. Although such a trench having a pit structure can be used for a pool or a skating rink, it is used, with difficulty, for other games including events for other purposes.